1. Field of the Invention
The present invention relates to apparatuses in which transport streams are recorded.
2. Description of the Related Art
For terrestrial digital broadcasting received by mobile phones, mainly their third generation (this broadcasting is called one segment), video data is encoded in accordance with H.264/AVC, and audio data is encoded in accordance with MPEG-2 AAC. Encoded video and audio data are called Elementary Streams (ES) and are multiplexed into transport streams in MPEG-2 SYSTEMS as Packetized Elementary Stream (PES) packets for transmission. Transport Stream (TS) packets are arranged in the transport stream. The TS packet can contain attribute information indicating the type of bit streams constituting video and audio information, the bit streams, and reference clock information called Program Clock Reference (PCR) and used to synchronize media. TS packets are transported by radio or wire.
A receiver records TS packets, and upon receiving a TS packet having PCR, uses PCR to control System Time Clock (STC) for clock synchronization with a transmitter. Specifically, the receiver extracts the value of the transmitter's PCR sampled at 27 MHz and compares it with the count value of the receiver's STC, to adjust STC (clock recovery). When the value of STC, counted by an STC counter, becomes equal to or greater than that of Presentation Time Stamp (PTS) contained in the TS packet, the receiver synchronously reproduces ES.
To more accurately synchronize the transmitter's and receiver's clocks, for example, Jpn. Pat. Appln. KOKAI Publication No. 2001-359049 proposes a scheme according to which, to delete a TS packet, the receiver generates a control packet and records packet deletion sections and the number of packets deleted, in the control packet. According to the proposal in Jpn. Pat. Appln. KOKAI Publication No. 2001-359049, the control packet enables an encoded program to be stream-reproduced in synchronism with streaming signals for transmission.
Proposal has been made of a technique for recording supplemental information such as PTS and reproduction time in a supplemental file. SD-Video for ISDB-TS has been known as a recording format for the supplemental file. With SD-Video for ISDB-TS, PTS is specified as a starting point (starting point PTS), and a reproduction time is calculated on the basis of the starting point PTS and each PTS in a TS packet. The reproduction time is then recorded in the supplemental file.
A timebase may be switched in the middle of a transport stream. PTS in a TS packet received after the switching of the timebase may deviate significantly from PTS in a TS packet received before the switching. Consequently, after the switching of the timebase, even the calculation of the reproduction time using PTS obtained before the timebase switching as a starting point PTS may disadvantageously result in a discontinuous value deviating significantly from the original reproduction time. In particular, if special reproduction such as skip reproduction is executed before and after timebase switching, it may disadvantageously not be executed normally. That is, the timebase switching may cause a value deviating significantly from the original reproduction time to be presented as a reproduction time for a recorded stream.
Therefore, it is not necessarily effective on the control of reproduction timings for TS packets to use PTS obtained before timebase switching as a starting point PTS to calculate a reproduction time and to record the reproduction time in a supplemental file.